Add a weak property type to the virtual machine.

runtime/vm/raw_object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 71 matching lines @@
       V(ExternalInt16Array)                                                    \
       V(ExternalUint16Array)                                                   \
       V(ExternalInt32Array)                                                    \
       V(ExternalUint32Array)                                                   \
       V(ExternalInt64Array)                                                    \
       V(ExternalUint64Array)                                                   \
       V(ExternalFloat32Array)                                                  \
       V(ExternalFloat64Array)                                                  \
     V(Stacktrace)                                                              \
     V(JSRegExp)                                                                \
+    V(WeakProperty)                                                            \
     V(Closure)                                                                 \
 
 #define CLASS_LIST(V)                                                          \
   V(Object)                                                                    \
   CLASS_LIST_NO_OBJECT(V)
 
 
 // Forward declarations.
 class Isolate;
 #define DEFINE_FORWARD_DECLARATION(clazz)                                      \
@@ skipping 81 matching lines @@
 // be dereferenced (e.g. RawSmi).
 class RawObject {
  public:
   // The tags field which is a part of the object header uses the following
   // bit fields for storing tags.
   enum TagBits {
     kFreeBit = 0,
     kMarkBit = 1,
     kCanonicalBit = 2,
     kFromSnapshotBit = 3,
-    kReservedTagBit = 4,  // kReservedBit{10K,100K,1M,10M}
-    kReservedTagSize = 4,
+    kWatchedBit = 4,
+    kReservedTagBit = 5,  // kReservedBit{10K,100K,1M,10M}
+    kReservedTagSize = 3,
     kSizeTagBit = 8,
     kSizeTagSize = 8,
     kClassIdTagBit = kSizeTagBit + kSizeTagSize,
     kClassIdTagSize = 16
   };
 
   // Encodes the object size in the tag in units of object alignment.
   class SizeTag {
    public:
     static const intptr_t kMaxSizeTag =
@@ skipping 50 matching lines @@
     ASSERT(!IsMarked());
     uword tags = ptr()->tags_;
     ptr()->tags_ = MarkBit::update(true, tags);
   }
   void ClearMarkBit() {
     ASSERT(IsMarked());
     uword tags = ptr()->tags_;
     ptr()->tags_ = MarkBit::update(false, tags);
   }
 
+  // Support for GC watched bit.
+  bool IsWatched() const {
+    return WatchedBit::decode(ptr()->tags_);
+  }
+  void SetWatchedBit() {
+    ASSERT(!IsWatched());
+    uword tags = ptr()->tags_;
+    ptr()->tags_ = WatchedBit::update(true, tags);
+  }
+  void ClearWatchedBit() {
+    ASSERT(IsWatched());
+    uword tags = ptr()->tags_;
+    ptr()->tags_ = WatchedBit::update(false, tags);
+  }
+
   // Support for object tags.
   bool IsCanonical() const {
     return CanonicalObjectTag::decode(ptr()->tags_);
   }
   void SetCanonical() {
     uword tags = ptr()->tags_;
     ptr()->tags_ = CanonicalObjectTag::update(true, tags);
   }
   bool IsCreatedFromSnapshot() const {
     return CreatedFromSnapshotTag::decode(ptr()->tags_);
@@ skipping 49 matching lines @@
   static bool IsByteArrayClassId(intptr_t index);
 
  protected:
   uword tags_;  // Various object tags (bits).
 
  private:
   class FreeBit : public BitField<bool, kFreeBit, 1> {};
 
   class MarkBit : public BitField<bool, kMarkBit, 1> {};
 
+  class WatchedBit : public BitField<bool, kWatchedBit, 1> {};
+
   class CanonicalObjectTag : public BitField<bool, kCanonicalBit, 1> {};
 
   class CreatedFromSnapshotTag : public BitField<bool, kFromSnapshotBit, 1> {};
 
   class ReservedBits : public BitField<intptr_t,
                                        kReservedTagBit,
                                        kReservedTagSize> {};  // NOLINT
 
   RawObject* ptr() const {
     ASSERT(IsHeapObject());
     return reinterpret_cast<RawObject*>(
         reinterpret_cast<uword>(this) - kHeapObjectTag);
   }
 
   intptr_t SizeFromClass() const;
 
   intptr_t GetClassId() const {
     uword tags = ptr()->tags_;
     return ClassIdTag::decode(tags);
   }
 
   friend class Api;
   friend class Array;
   friend class FreeListElement;
+  friend class GCMarker;
   friend class Heap;
   friend class HeapProfiler;
   friend class HeapProfilerRootVisitor;
   friend class MarkingVisitor;
   friend class Object;
   friend class RawInstructions;
   friend class RawInstance;
+  friend class Scavenger;
   friend class SnapshotReader;
   friend class SnapshotWriter;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(RawObject);
 };
 
 
 class RawClass : public RawObject {
  public:
@@ skipping 1050 matching lines @@
     return reinterpret_cast<RawObject**>(&ptr()->pattern_);
   }
 
   intptr_t type_;  // Uninitialized, simple or complex.
   intptr_t flags_;  // Represents global/local, case insensitive, multiline.
 
   // Variable length data follows here.
   uint8_t data_[0];
 };
 
+class RawWeakProperty : public RawInstance {
+  RAW_HEAP_OBJECT_IMPLEMENTATION(WeakProperty);
+
+  RawObject** from() {
+    return reinterpret_cast<RawObject**>(&ptr()->key_);
+  }
+  RawObject* key_;
+  RawObject* value_;
+  RawObject** to() {
+    return reinterpret_cast<RawObject**>(&ptr()->value_);
+  }
+
+  friend class GCMarker;
+  friend class MarkingVisitor;
+  friend class Scavenger;
+  friend class ScavengerVisitor;
+};
+
 // Class Id predicates.
 
 inline bool RawObject::IsErrorClassId(intptr_t index) {
   // Make sure this function is updated when new Error types are added.
   ASSERT(kApiErrorCid == kErrorCid + 1 &&
          kLanguageErrorCid == kErrorCid + 2 &&
          kUnhandledExceptionCid == kErrorCid + 3 &&
          kUnwindErrorCid == kErrorCid + 4 &&
          kInstanceCid == kErrorCid + 5);
   return (index >= kErrorCid && index < kInstanceCid);
@@ skipping 103 matching lines @@
          kExternalUint64ArrayCid == kByteArrayCid + 18 &&
          kExternalFloat32ArrayCid == kByteArrayCid + 19 &&
          kExternalFloat64ArrayCid == kByteArrayCid + 20 &&
          kStacktraceCid == kByteArrayCid + 21);
   return (index >= kByteArrayCid && index <= kExternalFloat64ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_